In recent years, highly integrated semiconductor devices have been sought after for use in high-performance and compact electron equipment such as cell-phones and IC cards. To obtain highly integrated semiconductor devices, fine semiconductor elements, and stack structures in which semiconductor elements are vertically stacked have been developed. For making such stack structures, adhesives are used for bonding between semiconductor elements. However, well-known adhesives such as an acrylic resin, epoxy resin, and silicone resin cannot be applied in the step for electrode assembly of metal bumps, an ion diffusion step, or other steps that require a high temperature of 250° C. or above because those adhesives are heat-resistant at temperatures only around 250° C.
Patent Document 1 discloses an isocyanurate ring-containing polymer that is used in an adhesive for optical semiconductors, and a composition containing the isocyanurate ring-containing polymer. This document discloses that the isocyanurate ring-containing polymer can be obtained by allowing an N-monosubstituted isocyanuric acid to react with a dihalogenated compound under the presence of an alkali metal compound, or by subjecting an N,N′,N″-trisubstituted isocyanuric acid and a silane compound to a hydrosilylation reaction. This document also discloses that the composition can be used as an adhesive for optical semiconductors, and can be heated in an oven at 50° C. to 250° C. for 30 minutes to 4 hours for bonding.
The market of flat panel displays (FPDs) such as liquid crystal displays (LCDs) and organic EL (OLED) displays are rapidly expanding. Although glass substrates are used as base materials of display panels in liquid crystal displays, flexible displays in which plastic substrates are used have been developed for obtaining thinner, light weight, and flexible displays, and reducing processing costs by employing Roll-to-Roll processes. However, PET resins, PEN resins, and PC resins known as resin materials used in well-known plastic substrates are heat-resistant at only around 250° C. The resin materials cannot be thus used in a process requiring a high temperature of 250° C. or above that is conventionally required in the step for forming thin film transistors (TFTs).
The process for forming thin film transistors includes a step for forming insulating films such as gate insulating films. Patent Document 2 discloses a gate insulating film forming agent for thin film transistors, with which gate insulating films can be formed at a temperature of 180° C. or below.